Linkello - Video calls simplified, no installation required.
Dasher Messenger - Dasher lets you do more than just text message. It's messaging with benefits:
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Green Messenger - WhatsApp Messenger Web for Chrome. Text/Chat on computer. Notifications, messages, tools.
Blab.im - Blab.im is a 4 person WebRTC (plugin free) video chat client and broadcasting people for up to 4...
Zulip - Chat for distributed teams. Zulip combines the immediacy of real-time chat with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones.